XLA Passes Document

[apivovarov]

Hello Everyone

I looked at the xla/docs folder and can not find a document describing XLA passes.

Do we need such document?
I started working on it and uploaded a draft version to the following location - https://github.com/apivovarov/openxla-xla/blob/passes_doc/docs/passes.md

Let me know what you think

Thank you
Alex P